Stabilization of high molecular weight organic material containing inorganic acid-forming elements



Patented Aug. 14, 1 951 STABILIZATION OF HIGH MOLECULAR. WEIGHT oRG NIcMATERIAL coN- .TAINING INORGANIC ACID-FORMING ELEMENTS 1 Willem LeendertJohannes de Nie, Englewood, N. J., and Heino Tonnis Voorthuis,Amsterdam, Netherlands, assignors to Shell Development Company,Emeryville, Calif., a corporation of Delaware No Drawing.

Claims. 1

This invention relates to the stabilization of high molecular weightorganic material containing inorganic acid-forming elements. More par-,ticularly the invention provides organic polymer compositions which havebeen rendered resistant to the changes in properties that arecharacteristic of such compositions Without any substantial loss oftransparency or moisture resistance. In its most specific embodiment theinvention provides a method of inhibiting the formation of freeinorganic acids within an organic mass by the thermo or photochemicallyinduced decomposition of organic polymeric molecules to which areattached inorganic acid residues.

Organic polymers and other high molecular weight organic materials arebecoming increasingly important in commercial applications. A large andimportant class of such substances are high molecular weight organicmaterials in which the residues of inorganic acids, as halogen atoms,the sulfate, phosphate, nitrate and similar groups are attached to oneor more atoms of complex organic molecules. Illustrative examples ofsuch materials are the halogenation products of fats, train oils, waxesand the high boiling hydrocarbons, such as naphthalene, diphenyl, andthe normally solid paraiilns; the polymers and copolymers of the vinylhalides, the vinylidene halides,

the halogenated dienes, the vinyl halide acetates,

the halogen acrylonitriles, the halogen methacrylonitriles and thefurther reaction products 01' the polymers and copolymers of suchmaterials with the halogens; the reaction products of the polymers andcopolymers of the alkenes with the halogens; the reaction products ofthe polyunsaturated compounds such as the natural rubbers, gutta percha,balata, polymerization and copolymerization products of the dienes, theacetylene hydrocarbons, the vinyl acetylene hydrocarbons and thediacetylene hydrocarbons, and including the derivatives of thesehydrocarbons with the halogens, S02, P203. N203, H2S and the hydrogenhalides and the like. These organic materials with which the inventionis concerned have molecular weights of at least 162. J

The problem of reducing the tendency of such materials to split offmolecules of an inorganic acid corresponding to the acidradical attachedto the, organic material is both serious and difflcult of solution. Forexample, in the case of the halogen containing vinyl resins, the mostdesirable fabrication techniques require that the plastic materialwithstand temperatures ap- Application March 2, 1951, Serial A In theNetherlands September 2 I proaching 200 C. during molding and formingoperations, and many of the most desirable applications of the formedplastic materials require that they withstand the efiects of directexposure to sunlight and moisture. In other words, the most importantuses of the materials often require their resistance to change under thevery conditions most liable to induce the complex molecules todisintegrate.

It has long been known that the incorporation of a, substance capable ofcombining with the inorganic acid as it is formed in such compositiongreatly improves the stability of the composition. White lead or basiclead carbonate, for

example, has been found to present a partial solution of the problem andbecause of its low cost has been so employed on a large scale. However,inorganic stabilizers such as white lead are not soluble in the organicmaterials and must be finely dispersed in the solid form throughout themass of organic material. Their employment, therefore, prevents theformation of transparent compositions and is not applicable for otherthan compositions which remain in the solid state. Numerous organicsubstances have been proposed, but the vast majority do not approachwhite lead in their stabilizing efliciency; further, many of them aretoo volatile to remain in the composition for a suflicient period oftime; many are themselves rapidly decomposed or discoloredphotochemically while others cause cross-linking between the polymerchains, thus changing the thermoplastic characteristics of the polymersin the composition.

Certain organic compounds containing an epoxide group have been found tobe effective thermostabilizers for high temperatures over short periodsof exposure. Thecompounds heretofore proposed which contained thisreactive grouping are the alkyl or aryl derivatives of the ethyleneoxides. The lower molecular weight compounds of this type, however, arerelatively volatile and will not remain in the plastic compositions forsufliciently long periods of time, and the higher molecular weightcompounds, while having a sufficiently low volatility andthermostabilizing efficiency, are readily decomposed or discolored bylight.

It is therefore a principal object of the present invention to provide amethod of stabilizing high molecular weight organic materials containingacid forming elements by the incorpoleast above 300 ration ofstabilizing materials which .to

the compo'sltionsa high resistance to: thermal decomposition thatismaintained over. a long period of time and which comparable to orbetter than the transparency of the composition. Another /object is theprovision or thermoplastic compositions in which the formation ofinorganic acids by the decomposition of polymeric molecules has beeninhibited by the incorporation of a light stable organic substancehaving a very high boiling .point. Another object is the provision of ahalogen containing vinyl resin composition containing a stabilizer whichis an oil soluble, water insoluble organic composition boiling at C. andwhich composition exhibits an increased resistance to the effects ofheat and/or light and exhibits properties or electrical resistance equalto or greater than the inherent properties the resin. Still otherobjects and advantages of the invention will be apparent from thefollowing description.

We have now discovered that, contrary to the general rule (that thepresence 01' a plurality of functional groups attached to a singlemolecule causes a decrease in the resistance of the molecule tophotochemically induced decomposition or discoloration), certain highmolecular weight organic compounds containing two or more epoxide groupsand having the structure defined below surprisingly exhibit 'a greaterstability than compounds of an identical structure, but containing asingle epoxide group.

The present invention may therefore be generally stated as providingmeans of increasingboth the thermal and photochemical stability of highmolecular weight organic materials of the aforementioned type containingcomplex molecules to which are attached the residues of inorganicacids.. The invention is particularly applicable for stabilization oforganic material which contains halogen as a structural component andtends to release hydrogen halide with concurrent decomposition-e. g.,polymers of vinyl halides. The inhibition of the heat and o! the lightinduced deterioration of the organic materials is effected byincorporating and intimately admixing therewith about 0.2 to 5% byweight oi! an epoxyalkyl pobether of a polyhydric phenol, whichpolyether has a boiling point above 300 C. under normal pressure (760mm. Hg). and which polyhydric phenol contains up to three phenolichydroxyl groups and also contains, besides the elements in its hydroxylgroups, only atoms of carbon and hydrogen. The epoxide structure in theepoxyalkyl radicals of the polyether has the oxygen atom with its twobonds linked to diflerent saturated carbon atoms which are vicinalcarbon atoms and are thus linked directly together as is the case in thegroup W"?- The epoxy structure can be in either terminal that obtained.by the employmentoi white lead without any substantial decrease in- 4these repoxygroups or epoxy oxygen atoms ina molecule of the polyetheris greater than 1.0

in being a value between 1.0-and 3.0. with the simple polyethers,- thenumber is the integer 2 or 3. Thus with 1,3-'bis(2,3-epo xypropoxy)benzene and with -1,li,5-tris(3,4-epoxybutoxy)benzene, the number ofepoxy oxygen atoms is 2.0 and 3.0, respectively,"pcr' molecule. with thecomplex polyethers which are a mixture of compounds of similar structurebut somewhat different molecular weight, the measured molecular weightof the mixture is an average, and therefore, the calculated number oioxygen atoms in an average molecule will not necessarily be an integer,but in any case will be a value greater than 1.0. The polyhydrio phenolfrom which th polyethers are derived contain two to three phenolichydroxyl groups. These hydroxyl groups can be linked to separate carbonatoms of a single aromatic ring, to separate carbon atoms or ditlerentparts of condensed aromatic rings, or to separate carbon atoms ofaromatic rings which are joined directly or by intervening aliphatichydrocarbon radicals. In general, it is preferred to employ epoxyalkylpolyethers of dihydric phenols. The polyethers used as stabilizers inthe compositions of the invention contain a plurality of up to threeepoxyalkyl groups, each of which are joined to aromatichydrocarbonradicals from the phenol by ethereal oxygen atoms.Accordingly, the stabilizer compounds have each of the oxygen atomstherein attached to two dif- Ierent atoms and are thus free of carbonylgroups with the result that they exhibit a pronounced resistance tophotochemically induced decomposition and thereby provide an unusuallymarked stabilizing action for the organic material which containshalogen as a structural component and tends to release hydrogen halidewith concurrent decomposition. Furthermore, the pohrethers aresubstantially non-polar organic compounds of high molecular weight andthereby exhibit properties of electrical resistance equal to or greaterthan the organic material to be stabilized. Examples of simpleepoxyalkyl polyethers of polyhydric phenols used in the compositions ofthe invention include: 1,3-bis(2,3-epoxypropoxy)benzene,1,3-bis(3,4-epoxybutoxy) benzene, 1,3,5-tris (3,4- epoxybutoxy) benzene,1,3-bis(3,4-epoxybutoxy) 5 (2,3 epoxypropoxy)benzene, 4.4 bis(2,3-epoxypropoxyldiphenyl, 4,4 bis(2,3 epoxypropoxy) diphenyldimethylmethaneand the like. These and similar compounds as well as more complexpolyethers are obtainable by reaction of a monohaloepoxyalkane such asepichlorohydrin and a basic-reacting compound with such polyhydricphenols as resorcinol, catechol, 2,2- bis(4-hydroxyphenyl)propane(bisphenol), 4,4- dihydroxydiphenyl, bis(2,2 dihydroxydinaph thyl)methane, and the like.

The glycidyl polyethers of dihydric phenols constitute a preferred classof stabilizers. Both the simple and complex polyethers of this class areof the general formula or interior location as present for example in a2,3-epoxypropyl (glycidyl) radical or a 2,3- epoxybutyl radical,respectively. The number of wherein n is an integer, and R is a divalentaromatic hydrocarbon radical free of other atoms than carbon andhydrogen. The simple diethers.

wherein n is zero are obtained by use of a considerable excess ofepichlorohydrin over the stoichiometric proportion of two mols ofepichlorohydrin per mol of dihydric phenol. Use of lesser proportions ofepichlorohydrin such as down to about 1.2 mols of epichlorohydrin perportance, as for example, in the preparation of opaque or colored solidcompositions to be continuously exposed to relatively high temperatures,the polyepoxide polyethers having a polymeric structure are particularlysuitable since they may be prepared to have a vapor pressuresubstantially as low as that of the plastic to be stabilized. Aparticularly suitable class of such ethers may be prepared by thereaction of a polyhydric phenol with an excess of a polyepoxide compoundsuch as an epoxyalkyl polyether of a polyhydric phenol to produce apolyepoxypolyhydroxy substance of a determinable molecular weight. Thereaction of the polyhydric phenols and polyepoxy compounds can readilybe accomplished by heating the reactants toin each case tested that theefficiency of the wherein n represents an integer greater than one.

The preparation of a glycidyl polyether of a" adding the basic catalystwas such that the reaction solution remained acid to phenol phthaleinthroughout the addition.

The cooled reaction mixture was freed of precipitated sodium chloride,and the organic portion fractionally distilled. A yield of 0.7 mols(70%) of resorcinyl bisglyoidyl ether was obtained in the form of acolorless, bright and viscous liquid, which after being left undisturbedfor some time at room temperature slowly crystallized. The ether wasreadily soluble in various organic solvents, but practically insolublein water, and had a melting point of from 33-36" C. and a boiling rangeof from 142-152 C. at 0.04 mm.

Since each glycidyl radical has an asymmetric carbon atom at least twodiastereo isomers can be formed fro-m each of the glycidyl polyethers.In the case of the diethers one of the isomers will be a racemic mixtureor racemate of the optically active d,dand 1,1- type, whereas the otherisomer will be of the 1,d-type which is optically inactive. The physicalproperties of the diastereo isomers often are sufficiently different toallow their easy separation, (in the case of the resorcinyl bisglycidylether, the isomers boil at 143 C. and 151 C., respectively, at 0.04 mm.pressure); further, the solubility of the isomers in organic solventsoften differs radically. glycidyl ether, while the lower boiling isomeris soluble in organic solvents the higher boiling isomer is practicallyinsoluble. However, though the solubility is radically different, it wasfound isomers as stabilizers are substantially the same.

For applications in which the solubility of the stabilizer in theplasticizer is not of primary imgether for a short time.- In generalreaction temperatures of around -250 C. can be used. The temperature andtime for any given reaction depend on .the proportions and reactivity ofthe reactants and whether the reaction is to be carried to completion orto an intermediate stage. In some cases it is advantageous to add tracesof basic catalyst such as caustic alkali to the mixtures of polyepoxideand polyhydric phenol, although in many, if not most cases, heat aloneis sufiicient to produce the required reaction.

The complex others may be incorporated into the composition by a widevariety of suitable procedures. They may be introduced as solutions ordispersions in one or more of the reactants prior to the polymerizationof the polymer, or they may be introduced subsequent to thepolymerization reaction by any of the pro- 5 cedures suitable for thedispersion or solution In the case of the hydroquinyl bisof an additiveingredient into a plastic composition.

The epoxyalkyl polyethers of the polyhydric phenols exhibit exceptionalefliciency as stabilizers and therefore may be employed in comparativelysmall quantities in the compositions of the invention. The amount of thestabilizing agent most suitable for a particular application will begoverned by many factors. In any case, a stabilizing amount whichinhibits the thermo and photochemical deterioration is used, and thisordinarily amounts to about 0.2 to 5% by weight of the organic materialbeing stabilized. The use of about 0.5 to 2% is usually adequate.Excellent results are obtained with 1, 2 and 3% by weight. If desired,amounts suflicient to have a plasticizing effect upon the organicmaterial or polymer may be used such as up to 50 parts of the polyetherper parts of the organic material, the parts being by weight.

Example I.-Comparative thermostabilization of polyvinyl chloride powdersSamples of powdered Geon 101 (polyvinyl chloride) were preparedcontaining the designated amounts of the various stabilizers. The lengthof time required for the evolution of hydrogen chloride from. thevarious samples when sub- 7 iected to a temperature of 200 C. is listedin the following table:

Stabilizer ga l of Stability m Quantity per oi powder gfig 100 g. P. v.0. at 200 0. sufbmty Nature m for 10 mlns. K 200 C.

None. 0. 0.00 4 phen l glycidyl other 1. 0 0. 007 8 3.0

o 4. 0 0. 027 20% alpha-naphthyl glycidyl other 2. 0 0. 010 14 2. 4 Do3. 0 0. 015 18 reaorcinyl bisglycidyl ether. 1. 0 0. 009 ll 1. 7 n d"i"l iii l fd'i' M18 roqu Y 8 Y Y ether 1. 0 0. 009 2. 0 0. 018 2. 00.010 2. 0 0. 052 2. 0 0. 020 2. 0 0. 007

Example IL-Comparative thermostabilization of polyvinyl chloride foilsUniiorm foils 0.15 mm. thick were prepared under identical conditionsdiffering from one to another only in the amount and type of stabilizerincorporated into the composition (each containing in addition to thestabilizer 100 parts by weight of Geon 101 and 50 parts by weighttricresyl phosphate and having been milled 3 minutes at 155 0.). Thetoils were supported in a carbon dioxide tree air current whilemaintained at a temperature of 170 C. and the time in minutes requiredin each case to cause an evolution of hydrogen chloride is listed below:

8 plasticizer and differing only in the presence of resorcinyl glycidyldiethers as a stabilizer in the amounts indicated were pressed into 1.2mm. sheets at the various temperatures. The colors of the sheets weremeasured by a Lovibond tintometer. 1

Quantity Color caressed in units or Stabiof the vibond scale User 0111-Pressing Polymer culatcd temperaon P. V tom, "0.

0., per Yellow red total cent Corvic Standard.... 0 130 2.0 0.7 2.7 Do 0140 2.0 0.7 2.7

0 150 brown spots 0 160 1 ll. 0 14. 0 26. 0 2 1. 9 0. 1 2. 6 2 2. 0 0. 72. 1 g 2 160 2. 0 i. 2 1. l 2 160 3. 6 1. 6 5. 2

Example V.Comparatioe thermal stabilization of polyvinyl chloridecompositions Geon 101 (polyvinyl chloride) 100 $0 Plasticizer(di-(2-ethylhexyl) phthalate) 50,

Stabilizer 2 The degree of discoloration upon aging is given in thefollowing table in the form of extinction ooeiflcients. This data may beconsidered relative and it should be remembered that the higher theStabilizer Initial 1101 Polymer Quantity separation Nature H00 [100afterg. g. g. e B P. V. C P. v.

Min. (loop 101 90 Do... algliia-naphthyl glycidyl ether. 3 0 0. 015D0... W ea 3 0 0.022 205 Do...-. resorcinyl bisglycidyl ether 2 0 0.018270 7 Example IV.-Color stabilization during high temperature processingby resorcinyl bisglycidyl ether Samples 01 polyvinyl chloride powder(Corvic value, the darker the sample. Samples with values above 10 aretoo dark to be measured accurately. Values on the commercial stabilizermarketed under the trade name V-l-N, which is described in ModemPlastics Encyclopedia" (1947), as a stabilizer for vinyl resins againstdiscoloration" and is believed to be strontium stearate, have beenincluded for comparison. The stabilizer denoted by letter A was theglycidyl polyether obtained by reacting bisphenol with epichlorohydrinas described hereinbefore with use of 2.04 mols of epichlorohydrin and2.14 moles 0 of sodium hydroxide per mol of bisphenol. The

glycidyl polyether reaction product had the structure describedhereinbeiore with a value for n oi about 1.3 calculated on the measuredmolecular weight of 710 for the product. The compositions standard)containing tricresyl phosphate as a 75 were compounded on a roll mill bymilling for about minutes at roll temperatures of 270 and 300 F.

Time of Aging A V-l-N EXTINCTION COEFFICgOIIZIgT AFTER AIR AGING A'lEXTINCTION COEFFICIOEONE AFTER AIR AGING AT 7 Days 14 Days EXTINCTIONCOEFFICIENT AFTER AGING IN U. V. LIGHT SPECIFIC RESISTANCE, OHM. CM.X10"AT 0.

1 Minute at 110 0 a l gi tted.

example VI.--Comparative thermal stabilization of polyvinyl chloridesheets Samples of the sheets were heated at 160 C. in

an oven in air for the times indicated in the table below. Thedevelopment of color in the samples was measured by comparison with thestandard slides of the Lovibond tintometer.

10 glycidyl ether of the keto-containing polyhydric phenol, 4,4 bis(2,3epoxypropoxy) benzo phenone, is inactive as a stabilizer. Furthermore,this ether was not compatible with the polyvinyl chloride because thesheets containing it were turbid. The sheets of the compositions of theinvention containing the diglycidyl diether of resorcinol were clear andtransparent which indicates complete compatibility of this ether.

This application is a continuation-in-part 01' our copendingapplication, Serial No. 774,660, filed September 17, 1947.

We claim as our invention:

1. A composition of matter comprising organic material having amolecular weight of at least 162 which contains halogen as a structuralcomponent and tends to release hydrogen halide with concurrentdecomposition in intimate admixture with from about 0.2 to 5% by weightof stabilizer therefor consisting essentially of an epoxyalkyl polyetherof a polyhydric phenol, which polyether has a boiling point above 300 C.under normal atmospheric pressure, and which polyhydric phenol containsup to three phenolic hydroxyl groups and also contains, besides theelements in said hydroxyl groups, only atoms of carbon and hydrogen.

2. The composition as defined by claim 1 wherein the epoxyalkylpolyether is a glycidyl polyether of a dihydric phenol.

3. The composition as defined by claim 1 wherein the organic material isa polymer of a vinyl halide, and the epoxyalkyl polyether is a glycidylpolyether of a dihydric phenol.

4. A composition of matter comprising a polymer of a vinyl halide havinga molecular weight of at least 162 in intimate admixture with from about0.5 to 2% by weight of stabilizer therefor consisting essentially of aglycidyl polyether of a dihydric phenol, which polyether has a boilingpoint above 300 C. under normal atmospheric pressure, and which dihydricphenol contains, besides the elements in its two phenolic hydroxylgroups, only atoms of carbon and hydrogen.

5. A composition of matter comprising a polymer of a vinyl halide havinga molecular weight above 162 in intimate admixture with from about 0.2to 5% by weight of stabilizer therefore consisting essentially ofglycidyl polyether of the formula.

Parts Heating time (minutes) Stabilizer gg g 0 wherein n is an integerand R is a divalent aroresin 15 45 matic hydrocarbon radical free ofother atoms than carbon and hydrogen. None o 6.0 23 30 30 6. Acomposition of matter comprising polygg f: 1'5 21 as M 16 vinyl chloridehaving a molecular weight above D6115:IIIIIIIIIIIIIS- 3.0 1.7 2.5 4.04.7 162 in intimate admixture with from about 0.2 z'aepuypmpuy to 57 byweight of stabilizer therefor consisting h 1.5 is 25 30 30 0 gy??? 3.012 20 30 30 essentially of glycidyl polyether of the formula Theforegoing results demonstrates that the o ooQoH-om-{o-nao-cm-onmncm-o-n-o-o-on- -dnm,

wherein n is an integer and R is a divalent aromatic hydrocarbon radicalfree of other atoms than carbon and hydrogen.

7. A composition of matter comprising a polymer of vinyl chloride havinga molecular weight of at least 162 in intimate admixture with from about0.2 to 5% by weight of stabilizer therefor consisting essentially ofglycidyl polyether or 4,4-dihydroxydiphenyldimethylmethane.

8. A composition 01' matter comprising poly-- vinyl chloride having amolecular weight of at least 162 in intimate admixture with from about0.5 to 2% by weight 01' stabilizer therefor consisting essentially of4,4'-bis(2,3-epoxypropoxy) diphenyldimethylmethane.

9. A composition of matter comprising a polymer of vinyl chloride havinga molecular weight of at least 162 in intimate admixture with from about0.2 to 5% by weight of stabilizer thereforconsisting essentially ofl,3-bis(2,3-e'poxypropoxy)benzene. v

10. A composition of matter comprisin D 3 vinyl chloride having amolecular weight of at least 162 in intimate admixture with from about0.5 to 2% by weight of stabilizer therefor consisting essentially of1,3-bis (2,3-epoxypropoxy) benzene.

WILLEM LEEN'DERT J OI-IANNES m: NIB. HEINO TONNIS VOORTI-IUIS.

No references cited.

1. A COMPOSITION OF MATTER COMPRISING ORGANIC MATERIAL HAVING AMOLECULAR WEIGHT OF AT LEAST 162 WHICH CONTAINS HALOGEN AS A STRUCTURALCOMPONENT AND TENDS TO RELEASE HYDROGEN HALIDE WITH CONCURRENTDECOMPOSITION IN INTIMATE ADMIXTURE WITH FROM ABOUT 0.2 TO 5% BY WEIGHTOF STABILIZER THEREFOR CONSISTING ESSENTIALLY OF AN EPOXYALKYL POLYETHEROF A POLYHYDRIC PHENOL, WHICH POLYETHERE HAS A BOILING POINT ABOVE 300*C. UNDER NORMAL ATMOSPHERIC PRESSURE, AND WHICH POLYHYDRIC PHENOLCONTAINS UP TO THREE PHENOLIC HYDROXYL GROUPS AND ALSO CONTAINS, BESIDESTHE ELEMENTS IN SAID HYDROXYL GROUPS, ONLY ATOMS OF CARBON AND HYDROGEN.